... in precise size ,high qulity and perfect finish on surface. Metal Screw is made by one of the CY ... 1.stamping material :steel ,aluminum,zinc,stainless steel,copper2.surface treatment:painting ,powder coating,polishing, threading, sand casting3. ... (enamel)6.Inspection: coordinate measuring machine, optical comparator, surface indicator, chemical element analysis, hardness testing, tensile testing, ...